The replacement of segments of human blood vessels with vascular grafts is well known in the art. Among the accepted and successful vascular graft implants are those which are formed from a biologically compatible material which retains an open lumen to permit the flow of blood through the graft after implantation.
Vascular prosthesis made of knitted or woven Dacron.RTM. polyester have been used for many years in a variety of constructions. Common textile prostheses, made from Dacron.RTM. polyester, are very porous and require preclotting with the patient's blood prior to surgery in order to prevent hemorrhaging after implantation. Recent developments have employed coating the prosthesis, which enables the prosthesis to be implanted without preclotting. Coatings of different materials have been used, including biodegradable materials such as albumin, collagen and gelatin, as well as non-biodegradable materials such as elastomeric polymers.
Greco et al., U.S. Pat. No. 4,879,135 issued Nov. 7, 1989 discloses vascular grafts with a coating, respectively, of an anionic or cationic surfactant and an oppositely charged drug bound to the surfactant. The surfactant and oppositely charged drug are ionically bound.
Greco et al, U.S. Pat. No. 4,444,133 and Greco et al, U.S. Pat. No. 4,740,382 disclose vascular grafts coated with a cationic surfactant (TDMAC) and a negatively charged antibiotic.
Hu et al, U.S. Pat. No. 5,032,666 issued Jul. 16, 1991 discloses vascular grafts having a coating of thermoplastic fluorinated polyurethane urea (FPUU) having free amino groups which are then reacted with heparin or other antithrombogenic agent to covalently bond the compound to the FPUU coating.
Mano et al., U.S. Pat. No. 4,229,838 issued Oct. 28, 1980 discloses vascular grafts having a coating of polyethyleneimine that has been water-insolubilized by cross-linking with heparin ionically bound to the polyethylemeimine.
Mano et al., U.S. Pat. No. 4,321,711 issued Mar. 30, 1982 discloses a vascular graft having an anticoagulant substance such as heparin bound to the inner surface and a porous elastomer coating on the outside of the graft which contains a substance which counteracts the anti-coagulant substance.
However, these various coating approaches do not solve the problem of reducing the porosity of the prosthesis at the time of implantation so as to obviate the need for pre-clotting procedures, while at the same time reducing the thrombogenicity of the prosthesis to prevent clotting after implantation and promote the build up of a thin, even, well-defined and well-adhered pseudo-intima in the prosthesis. Therefore, there is a need for a vascular prosthesis which exhibits low porosity at the time of implantation of the prosthesis in order to obviate the need for pre-clotting which does not require a substance that counteracts an anti-coagulant, but which also allows for rapid build up of natural tissue within the interstices of the fabric of the prosthesis to promote good healing and prevent clotting.